Guide posts are typically used to delineate the edge of a road formation, and assist a road user by indicating the alignment of the road ahead. Guide posts are normally not provided an urban roads that are well lit. However, they may be provided on unlit urban roads (kerbed or un-kerbed) with poor alignment or inadequate edge delineation, and are usually provided on all rural divided and undivided roads.
The guide posts are typically made from timber, metal or plastic, and support a delineator positioned approximately 1000 mm above ground level. Delineators are small retro-reflectors or panels of retro-reflective material which provide a coherent pattern of delineation of the edges of the road as an aid to night driving. The guide posts are often embedded directly into the ground, wedged into a ground sleeve, or welded to a flange and bolted to the road or traffic island.
The guide posts may be rigid, such that they will either fracture or remain intact when impacted by a vehicle. The guide posts may be semi-flexible, such that the guide post fails by bending when impacted by a vehicle. In either case, the guide posts will require maintenance intervention to restore them to their previous state.
Alternatively, the guide posts may be flexible. Such spring-back or recovery signage is known and generally comprises one of two types. The first type is an elastomer based product that uses a block of rubber, polyurethane or the like at a fulcrum point. Upon collision the guide post travels toward the ground by way of the elastic deformation of the elastomer material. When released the guide post comes back to a substantially vertical position. However, elastomer based products typically suffer from “flutter”, which is the tendency of the post to move around from either the wind generated by passing traffic or atmospheric wind. Flutter is undesirable as it makes signage difficult to read, can cause the post to momentarily lean into the path of oncoming traffic, and in extreme cases of atmospheric wind, the post can lean over into traffic lanes. Damage to the post usually requires the replacement of the entire assembly. Furthermore, after a number of deflection cycles, the block of rubber, polyurethane or the like used in elastomer based products tends to suffer from plastic deformation, and ceases to function effectively.
The second type is a mechanical product which uses a spring and cables to provide the self righting force, and generally uses a mechanical mechanism for the fulcrum. One example of this is provided by U.S. Pat. No. 5,199,814 (Clark et al.), which describes a short plastic post which is used for delineation of vehicle paths comprising facing truncated conical load bearing cells. One cell has its conical base secured to the ground and one cell has it conical base secured to an upstanding plastic post. The truncated tips of both cells bear against each other with their axes normally aligned. The post extends upwardly from the conical base and contains a compression spring which tensions two cables which pass through the two cells. The tensioned cables pull the tips of the two cells to urge the post to remain vertically aligned.
However, there are several drawbacks to Clark's configuration. First, the Clark apparatus is a unitary assembly, providing the self-righting apparatus and post as one. The small conical cell tips are not conducive to supporting a large or tall post. Further, the apparatus is not amenable to retrofit of typical guide posts. Second, the Clark apparatus requires replacement of substantially all of the apparatus even if it is only the post that has been damaged. Third, the Clark apparatus does not have an effective mechanism which ensures that the post returns to the correct orientation once in the vertical position. That is, the top and bottom cells may not correctly realign, such that the post is rotated with respect to the lower cell. Finally, the Clark apparatus is expensive to produce, due to the complexity of the configuration of the compression spring, tensioned cables and various cable passages.
Accordingly, it can be seen that a need exists for a flexible coupling designed and developed to overcome, or at least substantially ameliorate, the disadvantages and shortcomings of conventional couplings used for spring-back or recovery signage.